The first landscape curbing machines created in the early 80’s consisted of a ram that moved in and out plunging and pushing the concrete into a form. These machines worked well but had three little problems that needed to be to be addressed.
The first problem was that the dry concrete mix would not feed down in the hopper, the cement would create a bridge or arch of cement material over the ram. To break the arch of material you would be forced to turn your shovel over and using the butt end of the shovel, break the bridge of material. Another solution was to use a small shovel to spoon feed the curbing machine. With this solution there is never enough material in the hopper to create an arch. Both these solutions slowed down the curbing process. The person running the shovel feeding the machine dictated the speed of the entire crew.
The second problem was that any cement that slipped past the ram to the wrong side of the ram was wasted. The cement would build up on the wrong side of the ram until it came out the side and was deposited next to the curb. On some machines, 20% of the material was on the side on the curb and had to be buried or hauled away.
The third problem was poor compaction in the top half of the curb. The cement would fall to the bottom of the ram area and the ram would start forward, compacting the concrete at the bottom and then pushing the concrete into the top of the slipform. A lot of the time the ram would push and compact the bottom of the curb moving the machine forward before it squeezed and compacted the top half of the curb.
Most manufacturers of curb machines addressed these problems. Most of them solved the bridging problem by making the hopper bigger and having the ram move farther. In order to maintain compaction, because they were taking larger amounts of concrete with each cycle of the ram, the ram had to hit harder and faster. This made the machines jump with every impact of the ram. To keep the machines under control and from jumping up and leaving a mark in the curb or from jumping left or right with ever impact, the machines were made heavier.
Curb-King developed and patented the orbital ram machine with the self-feed hopper to solve these problems. The self-feed hopper solved the bridging problem by moving one complete wall of the hopper. This would break any bridge that formed.
The waste problem and the compaction problem were solved with the orbital motion. The ram comes in pushing the curb into the slipform, at the end of the stroke the ram wipes upward filling the top half of the curb. As the ram returns to the starting position it does so in a high position going over any material that squeezed behind the ram. With the next stroke most of the waste is put into the curb.
At about this time a new technology came on the scene, the auger landscape curb machine. Almost every manufacturer developed an auger machine. They were smooth, easy to use and created beautiful curb right out of the machine. They had one draw back that has almost eliminated the single auger landscape curb machine. The single auger can not create any pressure. If you plug off the end of the auger the concrete rotates with the auger without progressing. A curb machine needs to create pressure so that the machine rides on the curb not the ground. If the machine rides on the ground then every bump or hole in the ground is translated into the curb.
Curb-King had solved this problem with the patented twin auger machine. The patented twin augers create lots of pressure forcing the cement material into the slipform with an even constant force. This machine has solved the problems of a single auger and allows the curbing machine to ride over an uneven spot.
Curb-King went one step further with their twin auger curbing machine. They added vibration to the hopper and augers of the curbing machine. Vibration does a wonderful thing to cement. It makes it liquid. The concrete becomes semi liquid in the hopper and around the augers. As soon as the cement enters the slipform it returns to its semi solid state. This gives you a very strong compacted curb.
The Twin Auger with its vibrating hopper and augers is the state of the art in landscape curbing machines. It gives you the smoothness of an auger type machine with all the advantages of the ram type machine.
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